Field of the Invention: The present invention pertains generally to electrical or electronic switching apparatus and related methods. More specifically, the present invention relates to such switching devices and methods useful for arming and fire control of an explosive or pyrotechnic actuation or detonation device or the like, such as “safe and arm” systems.
State of the Art: There are many applications in which explosive or pyrotechnic actuation or detonation devices are used and wherein an explosive or pyrotechnic charge is detonated using an electrical or electronic switching device for actuation. Examples include such things as automotive airbag initiators, parachute harness connectors, and the like. In such devices, the switching device generally performs the functions of arming the device and, upon the appropriate instruction, applying electrical energy to the device to cause the explosive or pyrotechnic charge to detonate. In many applications, such as those in which the device is portable, this involves charging a capacitive device and then discharging the electrical energy in the capacitive device into the ignition or detonation apparatus. Examples of such devices are disclosed in U.S. Pat. No. 5,063,846, issued to Willis et al. on Nov. 12, 1991; U.S. Pat. No. 5,245,926, issued to Hunter on Sep. 21, 1993; U.S. Pat. No. 5,587,550, issued to Willis et al. on Dec. 24, 1996; and U.S. Pat. No. 6,173,651 issued to Pathe et al. on Jan. 16, 2001.
In many known switching devices of this type, a mechanical safe and arm device has been used to initiate a detonator or ordnance train comprising an explosive transfer system or line, which in turn initiates an initiator. In recent years, the use of semiconductor bridges as part of the initiator device has increased. Examples of such semiconductor bridge initiators are provided in U.S. Pat. No. 5,929,368, issued to Ewick et al. on Jul. 27, 1999 and U.S. Pat. No. 6,199,484, issued to Martinez-Tovar et al. on Mar. 13, 2001.
Although such systems generally have proven to be reliable, they often impose undesirable size, weight and/or cost penalties. The cost penalties may include not only the cost of the components themselves, but also parts and associated logistical costs, assembly costs, etc.
With any safe and arm system, safety and reliability are of paramount concern. Accordingly, any system that vies as a candidate to replace existing safe and arm systems must have sufficient safety and reliability engineered into the system. It is also important in many applications to have the ability to monitor all aspects of the system, or at least critical component status. Many existing systems, such as those described above, have only a limited capability to monitor system status, for example, only to the safe and arm component.